Actuation system with locking feature

ABSTRACT

A technique facilitates use of an actuator with a locking feature enabling selective locking of the actuator in a desired operational position. For example, the actuator may comprise a mandrel which can be used to shift a tool between operational positions. The mandrel is surrounded by a housing which creates a cavity. A magneto rheological fluid is disposed within the cavity and operates in cooperation with the mandrel to enable selective locking of the mandrel at a desired operational position or positions. Magnetic field can be generated via an electromagnetic coil or a permanent magnet to selectively increase the viscosity of the magneto rheological fluid to lock the mandrel at the appropriate operational position.

BACKGROUND

Downhole tools are employed in a wellbore via a tool string and operated during a specific well application. To facilitate performance of the specific well application, many downhole tools have more than one operational position and may be selectively shifted between operational positions. During milling operations, for example, fluid flow may be controlled by a downhole valve device which is shifted between operational positions to direct fluid flow to a milling tool or to divert the fluid flow to the annulus. The downhole valve device effectively has two modes of operation, namely a milling mode in which the fluid is directed at a high flow rate through the valve device to the milling tool and a circulation mode in which the fluid is diverted into the annulus by the valve device.

SUMMARY

In general, the present disclosure provides a system and method related to an actuator having a locking feature enabling selective locking of the actuator in a desired operational position. For example, the actuator may comprise a mandrel which can be used to shift a tool between operational positions. The mandrel is surrounded by a housing which creates a reservoir, e.g. cavity. A magneto rheological fluid is disposed within the cavity and operates in cooperation with the mandrel to enable selective locking of the mandrel at a desired operational position or positions. A selectively activated or applied magnetic field, activated or applied by an electromagnetic coil or a permanent magnet, may be used to selectively increase the viscosity of the magneto rheological fluid to lock the mandrel at the appropriate operational position.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate various implementations described herein and are not meant to limit the scope of various technologies described herein, and:

FIG. 1 is a schematic illustration of a well system including an example of an actuator with a locking feature, according to an embodiment of the disclosure;

FIGS. 2 and 2A are schematic illustrations, respectively, of an example of an actuator having a locking feature, according to an embodiment of the disclosure;

FIG. 3 is another schematic illustration of an example of an actuator when the actuator is locked in a specific operational position, according to an embodiment of the disclosure;

FIG. 4 is a schematic illustration similar to that of FIG. 3 but with the actuator unlocked in the specific operational position, according to an embodiment of the disclosure;

FIG. 5 is a schematic illustration similar to that of FIG. 3 but with the actuator unlocked in a different operational position, according to an embodiment of the disclosure;

FIG. 6 is a schematic illustration similar to that of FIG. 3 but with the actuator locked in the different operational position, according to an embodiment of the disclosure; and

FIG. 7 is a schematic illustration similar to that of FIG. 3 but with the actuator unlocked and returned to a previous operational position, according to an embodiment of the disclosure.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to provide an understanding of some illustrative embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

The disclosure herein generally relates to an actuator having a locking feature enabling selective locking of the actuator in a desired operational position. The actuator may be employed as part of or used in combination with a variety of tools. For example, the actuator may be incorporated into or used in combination with downhole tools deployed in a variety of downhole, well related applications. According to an embodiment, the actuator may comprise a mandrel used to shift a tool between operational positions. The mandrel is surrounded by a housing which establishes a reservoir, e.g. cavity. A magneto rheological fluid is disposed within the cavity and operates in cooperation with the mandrel to provide a locking feature which enables selective locking of the mandrel at a desired operational position (or positions).

Selective application of a magnetic field controls the viscosity of the magneto rheological fluid which, in turn, either locks the mandrel, e.g. resists motion of the mandrel, or allows the mandrel to move relative to the housing. In an embodiment, an electromagnetic coil may be used to selectively create a magnetic field which effectively increases the viscosity of the magneto rheological fluid, thus locking the mandrel at the appropriate operational position. In an embodiment, a permanent magnet may be used to create the magnetic field and an electromagnetic coil may be used to selectively deactivate the magnetic field created by the permanent magnet.

In one embodiment of a downhole application, the actuator is used to control a shiftable device positioned along a tool string. By way of example, the shiftable device may comprise a shiftable valve which controls flow of fluid delivered downhole along the tool string. The actuator may be used to control the operational position of a variety of valves in many types of downhole applications.

In a specific application, the actuator is used as part of or in combination with a multi-cycle circulation valve deployed downhole via coiled tubing to provide a high flow rate of circulating fluid during a milling operation. The multi-cycle circulation valve is actuated to provide two modes of operation referred to as a milling mode and a circulation mode. When in a milling mode, the fluid pumped downhole passes through the multi-cycle circulation valve and flows farther downhole to a bottom hole assembly having a milling tool. When the multi-cycle circulation valve is shifted to the circulation mode, the fluid flowing downhole is diverted into a surrounding annulus. The actuator described herein may be employed in such an application to control the shifting of the valve between milling mode and circulation mode. The locking feature of the actuator enables a dependable locking technique for securing the shiftable valve at a desired operational position or positions, e.g a milling mode position or a circulation mode position.

Referring generally to FIG. 1, an example of a well system 20 is illustrated as comprising a tool string 22 deployed in a wellbore 24. The tool string 22 comprises a shiftable device 26, e.g. shiftable valve, controlled by an actuator 28. The actuator 28 comprises a locking feature 30 which enables selective locking of the actuator 28, and thus the shiftable device 26, at a desired operational position or positions. In this example, the shiftable device 26 is part of or works in cooperation with a bottom hole assembly 32 which may comprise a variety of tools depending on the parameters of a given well application. In a milling application, for example, the bottom hole assembly 32 may comprise a milling tool 34.

In a milling application, the shiftable device 26 may comprise a valve, e.g. a multi-cycle circulation valve, which is selectively shifted between a milling mode and a circulation mode. When in the milling mode, the shiftable device/valve 26 receives fluid pumped down through tool string 22 and directs the flow of fluid to the milling tool 34. When the shiftable device/valve 26 is shifted via actuator 28 to the circulation mode, the fluid pumped down through tool string 22 is diverted to a surrounding annulus 36. In this application, the locking feature 30 may be actuated to selectively and temporarily lock the actuator 28, and thus the shiftable device/valve 26, in either the milling mode or the circulation mode. However, the locking feature 30 can be used to lock the actuator 28 at other or additional positions.

Referring generally to FIG. 2, an example of actuator 28 is illustrated along with an embodiment of locking feature 30. In this example, the actuator 28 comprises a mandrel 38 slidably positioned within a housing 40. The housing 40 is structured to form a reservoir 42, e.g. cavity. As illustrated, the cavity 42 is filled with a magneto rheological fluid 44. The magneto rheological fluid 44 may be retained in the cavity 42 by the interior surface of housing 40 and by a plurality of seals 46 disposed between housing 40 and mandrel 38.

In the embodiment illustrated, the magneto rheological fluid 44 is forced through a restricted passage 48 when the mandrel 38 is shifted with respect to housing 40. The restricted passage 48 is referred to as an orifice (or orifices) and the orifice 48 (or orifices) may be positioned along various types of passageways through which the magneto rheological fluid 44 is forced when mandrel 38 is shifted with respect to housing 40. In the illustrated example, however, the orifice 48 (or orifices) is located through an expanded region 50 of mandrel 38. In some applications, the expanded region 50 may be dynamically sealed with respect to the surrounding surface of housing 40 so as to force the magneto rheological fluid 44 to move through orifice 48 whenever movement of mandrel 38 occurs with respect to housing 40. However, orifice 48 may be positioned at other locations outside of mandrel 38 while remaining in fluid communication with the magneto rheological fluid 44 such that the magneto rheological fluid 44 is forced through the orifice 48 by movement of mandrel 38. The orifice 48 also may have a variety of sizes, shapes, numbers, and/or configurations depending on the parameters of a given application.

Referring again to the embodiment of actuator 28 illustrated in FIG. 2, the viscosity of magneto rheological fluid 44 is controlled by selectively establishing a magnetic field which acts on the fluid 44. By way of example, an electromagnetic coil 52 may be mounted proximate the magneto rheological fluid 44. According to one embodiment, the electromagnetic coil 52 is mounted for movement with the mandrel 38. For example, electromagnetic coil 52 may be mounted in expanded region 50 proximate orifice(s) 48. The electromagnetic coil 52 is selectively powered to create the magnetic field acting on magneto rheological fluid 44 via electrical power supplied through conductors 54, e.g. wires, coupled with a suitable power source 56. It should be noted that in some applications the electromagnetic coil 52 may be in the form of a plurality of electromagnetic coils.

When electromagnetic coil 52 is energized via electrical power supplied by conductors 54, the magnetic field is established and the viscosity of magneto rheological fluid 44 is increased substantially. Similarly, de-energizing the electromagnetic coil 52 by removing electrical power reduces or removes the magnetic field and decreases the viscosity of magneto rheological fluid 44. While the electromagnetic coil 52 is energized and the viscosity of magneto rheological fluid 44 is increased, flow of the magneto rheological fluid 44 through orifice 48 is restricted (due to the high viscosity) thus effectively locking mandrel 38 at that position with respect to housing 40. In an embodiment shown in FIG. 2a , the actuator 28 comprises an electromagnetic coil 52 and a permanent magnet 53. The permanent magnet 53 generates the magnetic field to increase the viscosity of the magneto rheological fluid 44 to place the mandrel 38 in a desired operational position and the electromagnetic coil 52, when energized, counters the magnetic field of the permanent magnet 53, reducing or removing the magnetic field generated by the permanent magnet 53, thereby decreasing the viscosity of magneto rheological fluid 44, and allowing the mandrel 38 to be moved and/or placed in another desired operational position.

Depending on the parameters of a given application, the mandrel 38 may be shifted by a variety of mechanisms while the magneto rheological fluid 44 is in a low viscosity state. In the illustrated embodiment, the mandrel 38 has an interior passage 58 which effectively provides a mandrel orifice 60 through which fluid may be flowed to bottom hole assembly 32 or to other components farther downhole relative to actuator 28. In drilling applications, for example, fluid pumped down through an interior of tool string 22 may be flowed through mandrel orifice 60 and interior passage 58 to the milling tool 34.

By establishing a sufficient flow of fluid through mandrel orifice 60 and interior passage 58, pressure builds against mandrel 38 until a sufficient force is established to shift the mandrel 38 in the direction of fluid flow. In the illustrated example, this motion of mandrel 38 is resisted by a spring member 62, e.g. a coil spring or other suitable spring. The spring member 62 may be positioned to act against, for example, a shoulder 64 of mandrel 38. In this example, a sufficient force is created by fluid flowing through orifice 60 and acting against mandrel 38 to overcome the friction force of seals 46 and the counteracting spring force established by spring member 62. However, when the flow through orifice 60 is sufficiently reduced, the force applied by spring member 62 is able to shift the mandrel 38 back in an opposite direction relative to housing 40.

As described above, however, applying power to electromagnetic coil 52 increases the viscosity of magneto rheological fluid 44 and effectively locks the mandrel 38 at that position because the viscous magneto rheological fluid 44 does not readily pass through orifice 48. The forces exerted either by fluid flowing against orifice 60 or by spring member 62 are not sufficient to overcome the resistance to movement of mandrel 38 provided by the combination of the viscous magneto rheological fluid 44 and orifice 48. It is understood that the amount of power applied to the electromagnetic coil 52 may be varied and/or variable, which thereby varies the viscosity of the magneto rheological fluid 44 and allows the magneto rheological fluid 44 to provide a force to resist movement of the mandrel 38, acting in a manner similar to, for example, a shock absorber or the like.

Referring generally to FIGS. 3-7, an operational example is illustrated. In this example, the shiftable device 26 comprises a valve 66 which may be shifted by actuator 28 between a closed position, as illustrated in FIGS. 3, 4, 7, and an open position, as illustrated in FIGS. 5, 6. The actuator 28 may be employed to shift a variety of devices 26, e.g. a variety of valves 66, between operational positions according to the parameters of a given application. By way of example, the valve 66 may be used in a milling operation and may be in the form of a multi-cycle circulation valve shiftable between milling and circulation modes.

To facilitate explanation of the use of actuator 28 and locking feature 30, a milling operation example is described but such example should not be limiting with respect to the various uses of actuator 28 and locking feature 30. With respect to the milling operation example, FIG. 3 illustrates the configuration of actuator 28 when the well system 20 is in milling mode and fluid is pumped down through interior passage 58 of mandrel 38 to the milling tool 34. When in milling mode, power is sent to the electromagnetic coil 52 to generate the desired magnetic field and thus to increase the viscosity of the magneto rheological fluid 44. As a result, the drag coefficient of the magneto rheological fluid 44 passing through the orifice 48 is substantially increased and this locks the mandrel 38, e.g. prevents the mandrel 38 from shifting to the circulation mode.

When it is desired to shift from milling mode to circulation mode, electrical power sent to the electromagnetic coil 52 is disconnected. As a result, the viscosity of the magneto rheological fluid 44 and the drag coefficient of the magneto rheological fluid 44 passing through orifice 48 are reduced, as illustrated in FIG. 4. While the magneto rheological fluid 44 is in this lower viscosity state, the mandrel 38 may be shifted from milling mode to circulation mode, as illustrated in FIG. 5. In circulation mode, the valve 66 has been shifted to an open position which allows fluid moving down through interior passage 58 to be diverted to the surrounding annulus 36. In some applications, the valve 66 comprises radial ports through mandrel 38 which are moved beyond a seal 68 as the shiftable device 26/valve 66 is transitioned from milling mode to circulation mode. The shifting of mandrel 38 from milling mode to circulation mode may be achieved by generating a sufficient differential pressure at mandrel orifice 60 to overcome the resistance or counterforce provided by spring member 62 and the friction of seals 46.

After shifting to circulation mode, electrical power is again sent to the electromagnetic coil 52 to generate a magnetic field which again increases the viscosity of the magneto rheological fluid 44, as illustrated in FIG. 6. The high viscosity state of the magneto rheological fluid 44 locks the mandrel 38 with respect to housing 40 to maintain the circulation mode position. While power is applied to coil 52, the actuator 28 is prevented from shifting back to the milling mode even if the pumping of fluid down through interior passage 58 is stopped or if the differential pressure acting at mandrel orifice 60 is lost due to, for example, a change of pumped fluid density. At this stage, the drag coefficient of the magneto rheological fluid 44 moving through orifice or orifices 48 is greater than the force acting on mandrel 38 by spring member 62.

When it is desired to shift from circulation mode to milling mode, the pump rate with respect to fluid flowing through mandrel orifice 60 is reduced to decrease the differential pressure acting against mandrel orifice 60. Additionally, electrical power supplied to the electromagnetic coil 52 is disconnected to interrupt the magnetic field and to reduce the viscosity of the magneto rheological fluid 44. At this stage, the force generated by spring member 62 is sufficient to overcome the drag of the magneto rheological fluid passing through orifice(s) 48 and the friction resistance provided by seals 46 so as to shift mandrel 38, as illustrated in FIG. 7. In this particular example, the shifting of mandrel 38, as illustrated in FIG. 7, represents the transition from circulation mode back to milling mode.

The actuator 28 with its locking feature 30 may be used in a variety of well and non-well related applications to provide a simple technique for locking the actuator, and thus locking a shiftable tool, in a desired operational position. In well applications, the actuator 28 and locking feature 30 may be used to control fluid flow control devices, e.g. valves, or other devices depending on the specifics of a given application. In flow control applications, the locking feature 30 (in the form of, for example, magneto rheological fluid 44 and orifice 48) may be used to secure valve 66 in open flow or closed flow configurations. In milling applications, for example, the valve 66 may comprise or be part of a multi-cycle circulation valve system to facilitate locking of the system in selected modes, such as a milling mode or a circulation mode.

Depending on the application, the tool string 22 may comprise many types of components and systems selected for carrying out a given operation or operations. Similarly, the actuator 28 may be formed in various configurations with various styles of mandrel, housing, seals, electromagnetic coil, and/or other features. Similarly, the composition of the magneto rheological fluid may be adjusted according to the structure of the actuator 28 and/or the environment in which the actuator 28 is to be utilized. Additionally, electrical power may be supplied by a variety of power sources 56 at appropriate levels selected according to the type, number and configuration of the electromagnetic coil or coils which form electromagnetic coil 52. In an embodiment(s), the actuator 28 may be configured to lock the mandrel in more than two desired operational positions, as will be appreciated by those skilled in the art. In an embodiment, the magneto rheological fluid 44 may act as a shock absorber or the like wherein it exhibits resistance to flow but does not flow freely, etc.

Although a few embodiments of the system and methodology have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims. 

What is claimed is:
 1. A system for controlling actuation, comprising: a tool string deployed in a wellbore, the tool string comprising: a shiftable device; and an actuator having a mandrel slidably positioned through a housing and coupled with the shiftable device, the housing containing magneto rheological fluid in a manner such that shifting the mandrel with respect to housing causes movement of the magneto rheological fluid, the actuator further comprising a device for selectively establishing a magnetic field to change the viscosity of the magneto rheological fluid to resist movement of the mandrel relative to the housing.
 2. The system as recited in claim 1, wherein the shiftable device comprises a valve.
 3. The system as recited in claim 1, wherein the shiftable device is part of a multi-cycle circulation valve and wherein the tool string further comprises a milling tool.
 4. The system as recited in claim 1, wherein the actuator further comprises a spring member acting against the mandrel to bias the mandrel in a given direction.
 5. The system as recited in claim 1, wherein the mandrel comprises an orifice through which the magneto rheological fluid passes during shifting of the mandrel with respect to the housing.
 6. The system as recited in claim 4, wherein the device for selectively establishing a magnetic field comprises an electromagnetic coil or an electromagnetic coil and a permanent magnet.
 7. The system as recited in claim 6, wherein the mandrel is shifted against the bias of the spring member by establishing a sufficient fluid pressure at an opposite end of the mandrel.
 8. The system as recited in claim 7, wherein the shiftable device comprises a valve and the valve is opened and closed via shifting of the mandrel under the influence of either the sufficient fluid pressure or the force exerted by the spring member, the shifting being enabled while the coil is not energized and the magneto rheological fluid is in a lower viscosity state.
 9. The system as recited in claim 8, wherein the coil is energized to establish the magnetic field, thus locking the mandrel and the valve in an open state or a closed state via the increased viscosity of the magneto rheological fluid.
 10. A method for controlling actuation, comprising: providing an actuator with a shiftable mandrel; operatively coupling the shiftable mandrel with a volume of magneto rheological fluid such that movement of the shiftable mandrel forces the magneto rheological fluid through an orifice; connecting the mandrel to a well device which controls flow of fluid in a wellbore; and selectively changing the properties of a magnetic field to change the viscosity of the magneto rheological fluid to and change a resistive force applied by the magneto rheological fluid to the mandrel.
 11. The method as recited in claim 10, further comprising applying the actuator and the well device downhole via a tool string.
 12. The method as recited in claim 11, further comprising using the tool string to perform a milling operation.
 13. The method as recited in claim 12, further comprising using the actuator to selectively actuate the well device between a milling mode and a circulation mode.
 14. The method as recited in claim 13, wherein selectively changing comprises using an electromagnetic coil, or using an electromagnetic coil and a permanent magnet to temporarily lock the mandrel and thus the well device in at least one of the milling mode or the circulation mode.
 15. The method as recited in claim 10, wherein operatively coupling comprises moving the shiftable mandrel through a cavity containing the magneto rheological fluid.
 16. The method as recited in claim 15, further comprising sealing the magneto rheological fluid within the cavity via a surrounding housing and a plurality of seals.
 17. The method as recited in claim 14, further comprising mounting the electromagnetic coil or the permanent magnet for movement with the shiftable mandrel.
 18. A system, comprising: an actuator having: a mandrel comprising an orifice; a housing surrounding the mandrel to create a cavity; a magneto rheological fluid disposed in the cavity such that movement of the mandrel relative to the housing forces the magneto rheological fluid through the orifice; and an electromagnetic device selectively energized to increase the viscosity of the magneto rheological fluid in the cavity so as to resist movement of the mandrel relative to the housing.
 19. The system as recited in claim 18, further comprising a well device coupled to the mandrel and adjustable between operational positions via movement of the mandrel.
 20. The system as recited in claim 19, wherein the well device controls fluid flow in a downhole milling operation. 